1. Field of Invention
The techniques and apparatus described herein relate to semiconductor structures having an electrode structure in which conductive regions are recessed in a semiconductor region, and particularly to semiconductor devices, such as nitride-based semiconductor devices, using one or more such electrode structures.
2. Discussion of the Related Art
Improved power transistors are desired for advanced transportation systems, more robust energy delivery networks and new approaches to high-efficiency electricity generation and conversion. Such systems rely on very efficient converters to step-up or step-down electric voltages, and use power transistors capable of blocking large voltages. In hybrid vehicles, for example, power transistors with blocking voltages of more than 500 V are used to convert DC power from the batteries to AC power to operate the electric motor.
Conventional power devices (e.g., transistors or diodes) used in such applications are made of silicon. However, the limited critical electric field of silicon and its relatively high resistance causes available commercial devices, circuits and systems to be very large and heavy, and operate at low frequencies. Therefore such commercial devices are unsuitable for future generations of hybrid vehicles and other applications.
Nitride semiconductor devices have been proposed as offering the potential for producing high-efficiency power electronics demanding high blocking voltages and low on-resistances.